Hello People,

2000 LS MGM's ATC (Automatic Temperature Control) is blowing hot air. It is switching from FLOOR to FLR-DEF and to all other directions, but it is NOT switching from HOT to COLD.

So even if its showing 60 degrees its blowing HOT.

Two mechanics told me that this is PROBABLY caused by the duct door that does not open for COLD air.

One mechanic told me that he is PRETTY SURE this is faulty ATC itself.

What is your opinion?

Thank you in advance,
2OOOLS
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Unfortunately, after re-connecting another ATC, problem exists.

Mechanic told me that this is possible brakedown of some kinda door that switches between hot or cold air.:-)

If you know what I am talking about your help would be highly appreciated.

In the mean time, I am slowly starting to remove my dash piece-by-piece...

TIA
2OOOLS
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i think they said about broken blend door or faulty blend door motor.

so my question is what should I remove for changing blend door?
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I would check ALL the vacuum hoses before doing major surgery you are suggesting. Had a similar problem on an '87 LS and it was a hose! Since you sound as if you are going in there anyway it wouldn't hurt to test them all!! MB
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thanks miamibob,

all hoses checked. system is working. however its not switching between hot and cold :-)

any ideas where this blend door could be?
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I would suggest a good book like HELMS or something similiar that can give you close up diagrams. If you have never done this before I would not suggest the repair. Too many things to remove and too many chances to REALLY screw something up....unless you are an automotive jock.....MB

P.S. Try the library if you do not wish to buy a book. Could also try the repair sections of AUTOZONE.COM or something close!
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thanks miamibob,

I am not a automotive jock. But its too late anyway. I/P is already removed...

The thing is that I looked in the Haynes book for my car yesterday (before removing Instrument Panel) at the local Autozone and to be honest was not impressed. Its $17 but it did not cover, for example, removing I/P. So I decided to skip it. Anyway i want be able to get it for few days until my I/P will be on place.

Instead I ordered CD called "2000 MERCURY GRAND MARQUIS CD WORKSHOP REPAIR MANUAL" which covers a lot of stuff. For example, using its 50 step guide I removed I/P successfully, where every step comes with the picture and description to it and what to do. However, it took me anyway about 8 hours to do that.

So when I finally removed I/P I found out myself before question of what to do next? To be honest I was expecting to see some physical damage. I would just replace the part and put damn I/P back. But some things are unclear for me now.

This is what I got to see:
Image

Image

My rough guess that this thingy is A/C Blend Door Actuator:
Image

Image

That door (Actuator's) is hardly moving. Is it suppose to be like that?
Image

Image

Image

Image

Is there any way to test if its (A/C Blend Door Actuator) good or bad one?
Or should I remove it along with the door and inspect for damage?

Thank you in advance,
2OOOLS
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I believe those doors ONLY move (or should only BE moved) by the Actuators involved - by vacuum power or electrical (depending upon the year). By the way, those photos are EXCELLENT!! They are very detailed - maybe you could build a Site or write a short book when your work is completed. Let us all know how you make out!! MB
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Ok, job is done!

Everythng is working just as it suppose to!

Here is the TIP:

If you are complaining that you have no temperature control (with or without a "clicking" sound behind the glove box area) and suspecting temperature blend door actuator you would need to do a:

Electronic Automatic Temperature Control (EATC) Module SELF-TEST

- The EATC module SELF-TEST will not detect concerns associated with data link messages like engine coolant temperature or vehicle speed signals. A scan tool must be used to retrieve these concerns.

- The EATC module SELF-TEST will detect concerns in the system control functions and will display hard diagnostic trouble codes (DTCs) in addition to intermittent diagnostic trouble codes for concerns that occur during system operation. The vehicle interior temperature should be between 4º-32ºC (40-90ºF) when carrying out the self-test. If the temperatures are not within the specified ranges, false in-car temperature sensor DTCs will be displayed.

- The SELF-TEST can be initiated at any time. Normal operation of the system stops when the self-test is activated.

- To enter the SELF-TEST, press the OFF and FLOOR buttons simultaneously and then press the AUTOMATIC button within two seconds. The display will show a pulse tracer going around the center of the display window. The test may run as long as 30 seconds. Record all DTCs displayed.

For example, in case when I had faulty A/C Blend Door Actuator I had 024 and 025 codes displayed.

- To exit the SELF-TEST and clear all DTCs, press the DEFROST button. The vacuum fluorescent display window will show 888 and all function symbols for one second. Then, the EATC control assembly will turn OFF (display blank) and all DTCs will be cleared.

- Always exit the SELF-TEST before powering the system down (system turned OFF).

When I replaced the faulty Actuator with new one I just did the SELF-TEST one more time. This time I had NO codes but all function symbols displayed at once indicating that I dont have any problem.

I also looked at the Actuator with flash light through glove box and that white tip was slowly moving as I changed temperature.

Good luck to you all,
2OOOLS

PS. Btw, if some of you (NY or NJ) have similar problem like I had and dont know how to hanlde it I will be more than glad to come to your place and help you out :-)
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Love them computers. Does anyone know if there is an EATC Module self test for a 1998 Grand Marquis?
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Image


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What tester did the above screen output come from? MB
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OTC Genisys


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Good news. While warming up the motor prior to conducting the Self-Check, I was switching back and forth between settings and I could hear the gate opening and closing each time I switched settings, indicating that physically the gate and the related motor were operating. So I ran the Self-Check and it apparently reset the computer part of the system and it went back to normal operation. Hope it lasts. Love them computers. Old Sarge.
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Hi there, really glad I found this site and thread. I have the same problem with the AC. Was fine yesterday morning on the way to work and when i went to lunch, boom, blowing way hotter than the outside air. of course, here in phoenix, its gonna get rough here very soon. i ran the self test and it came back with code 025 only. I haven't been able to find out what that particular code is. I took it to big o last night and the guy said he thought it was the entire ATC panel that cost 650 to replace since he had to do it on his thunderbird once. He said that I would have to order that part just to test and plug it in and see if it fixed and its not worth the chance because you can't return. He suggested I take it to the dreaded dealer instead, at least it didn't cost me anything. Anyway, if anyone can advise on that code 25 it would be appreciated. Interestingly, now it seems to be stuck in Defrost, ie, blowing up the front windshield and no matter what i press vent/max a/c buttons, I can't get it to blow air out of the vents. Weird. I am going to run self test again for the hell of it and see if that fixes it or if I get any new code. Thanks for any/all replies. Steve in Gilbert,AZ
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